2-pyrrolidone-5-carboxamide derivatives and methods of preparing the same



Patented Sept. 8, 1953 Z-PYRROLIDONE-S-CARBOXAMIDE'DERIVA- 'rrvns AND METHODS OF PREPARING THE SAME Robert Bruce Angier, Pearl River, N. Y., assignor to American 'Cyanamid Company, New York, N. Y., a corporation of Maine No I raw ing. App i(r t v Aug-1515.22, 195. 1,. Serial No. 243,155 I, v

This invention relates to certain new N -aralkyl-2-pyrrolidone-5-carboxamides and methods of preparing the same. The new compounds of this invention may be represented by the following general formula:

in which R1 represents hydrogen or at least one a -14 Claims; (chase-326.3)

halbgeh radicals with which the phenyl nucleus lower alkyl substituent connected to carbon in the pyrrolidone nucleus, R2 represents hydrogen or at least one substituent selected from the group consisting of halogen and loweralkyl, and in which R3 represents a methylene (-CI-Iz-Q group. A substituent or substituents represented M by R1 may be in any or all of the 3, 4 and 5 positions of the pyrrolidone nucleus, and a substituent or substituents represented by R2 may be any of the ortho, meta, or benzene ring.

The new compounds of this invention have been found to have anticonvulsant activity in para positions of the may be substituted may be illustrated by chlorine and bromine. 1

To determine the anticonvulsant activity of the new compounds of this invention, tests were made upon rats which had been treated with one of the compounds to determine their resistance to artificially induced convulsions. The resistance of rats, whichhadbeentreated with a given compound, to sound which ordinarily causes them" to convuls evwas first'determined and if the ij'pyrrolidone "compound showed, unusual promise in this test, the resistance of the rats to electroshock was then tested. In the audiogenic test, a rat was treated with a given pyrrolidone compound and after allowing a reasonable period for absorption the rat was subjected to the noise .,created by a" blast of air upon a series of bafiles for from 16 seconds to 60 seconds. which had shown a susceptibility to convulsions under these conditions by at least 3 previous con- Only rats vulsions on 3 preceding days were employed in "the test. 'In' other words, before a pyrrolidone compound was rated as active it must have prerats. This is indeed ,unexpected in View of the fact that extremely closely related compounds have been found to be entirely lacking in such activity. For instance in theabove formula Rs must represent a methylene group since compounds in which R3 represents other groups such as ethylene or substituted methylene have failed to show the desired activity; Likewise if the methylene group is missing so that one has aphenyl substituted amide, thecompoundsfail to show the desired activity. Loss of activity can vented or limited the intensity of a convulsion in a rat, which rat had previously been shown to be subject to convulsions under the conditions em- -ployed.'- In the electroshock treatment, the activity of a compound was determined by its ability to prevent or lessen the severity of a convulsion under conditions which had been previously shown on 3 preceding days to cause convulsions in th'e'individual rats tested. Such procedures for testing a compound for anticonvulsant activity areyvell known and widely accepted by those skilled in the art and since they do not constitute also be produced by substituting the l-nitrogen 5 in the pyrrolidone nucleus. In other words, only a very narrow class of N -aralkyl2-pyrrolidone- 5-carboxamides have 'shown' the property of having anticonvulsant activity. Lower alkyl substituents on the 3, 4 or 5 position of the pyrroli done nucleus do not appear to materially afiect the activity of the compounds to any appreciable extent although the effective dosage is sometimes lower in compounds having such substituents.

Likewise, substituents upon the phenyl nucleus of the types listed above as a general rule do not materially afiect the activity although some compounds in Which the phenyl nucleus is substituted appear to be less active and require a higher dosage than compounds in which the phenyl group is unsubstituted. Lower alkyl radicals with which, the pyrrolidone and phenyl nucleus may suitably bev substituted may beillustrated by methyl, ethyl, and propyl radicals, and

'an essential part oi the present invention will not be described in greater detail.

The following table lists the activities of various pyrrolidone compounds in controlling convulsions in rats ordinarily produced by sound (audiogenic) and also, in some instances, the compounds activity in controlling convulsions ordinarily produced by electroshock. All of the compounds tested may be represented by the following formula:

R NHR5 in which R4 and R5 represent radicals as indicated in the table. A rating of 4 plus is given to compounds which completely prevented convulsions or which prevented convulsion except during actual excitement: a rating of 3 plus is given to compounds which prevented convulsions except duringactual excitement or only momentarily after excitement was terminated: a rating of 2 "his or 1 plus was given to compounds which caused the rats to have convulsions to a less degree or for a shorter period of time after excitement was terminated. The-dosages given .inthe tablee are:izi-imilligxams of icompOund peri kilograms of body weight. If the compound was given orally it is so indicated and if given by? injection it is indicated by ipi after the dosage in milligrams.

4 since compounds which should be more readily absorbed in the animal body do not show the same desired degree of anticonvulsant activity.

Of course, the new compounds of this invention have:otherautilityend maybe-"employed in many varied fields-of chemistry: Forlirista'nce the new compounds may be employed as plasticizers for cationic melamine resins.

It is one of the advantages of the present inventiofi.*:that-the--new *compounds thereof may be In the above-table'it will be se'enethat of-- the-'2- pyrrolidone-5-carboxamides tested only ,the nar row class constitutingethetsubject 'mattei of: this invention dis play the valuableproperty bf having anticonvulsant activity. 65'

The reason for the extraordinary effect of the benzyl or substituted benz'yl group is not fully understood, nor has it'been' determined why other groups quite'similar td the onzyl or substituted benzyl group do not give compoundshaviiig anti 70' convulsant activity. Itis, there'for'emot intended that the present"invention beiliffiited to -any theory with regardto theactivity of t ne'w compounds." Itseems"reasoneibly '"certain,'*howprepared by :"any kofaseveral methods: For". in stance; the new compounds mayo-be prepared-"by heating a b enzyl amine' or the appropriately .sub'-: stituted derivative thereoflwith am-ester of: the appropriate- 2-pyrrolidone-carboxylic acid; This method may .rbe'iem'p'loyed" fon'preparing any .301 the new' com'p'ounds of this .inventioniand is the preferred m'ethod for prepariiig :co'mpo'unds' sin whicl i the pyrroli'done nucleus -is highly substi= tut'edL- For:instancd this method is the preferred method for preparing- 3,3,5-trimethy1-N -benzyl4 2 pyrrolidone fi-carbox'amide; I

A second metho'd hasralso been discoveted ior preparing the compoundsot the eIa-ssrepresented ever, that iii-is pw questiofi of absorptibn 75" by the 'above general-formula. This'l-imethodlis preferred for preparing compounds in which the pyrrolidone nucleus is unsubstituted and it is intended that this new method also constitute a part of the present invention. This new method comprises reacting a benzyl amine or the appropriately substituted derivative thereof with diesters of glutamic acid or the appropriately substituted derivatives thereof. The new reaction may be illustrated by the following equation:

in which Re and R7 represent esterifying radicals; R8, R9, R10 and R11 represent the same or different members selected from the group consisting of hydrogen and lower alkyl radicals; and This as defined above.

The reaction may be performed in an inert solvent or if desired it may be performed in the absence of a solvent. The preferred procedure comprises employing an excess of the aralkyl amine reactant as a solvent. Other materials which may suitably be employed as solvents may be illustrated by acetone, ethyl alcohol, dioxane and chloroform. The reaction may be performed over a wide range of temperatures, for instance from room temperature up to the reflux temperature of the benzyl amine or the solvent employed. In fact, if desired, the reaction may be performed at temperatures below room temperature, for instance 10 C. At room temperature, about 2 to 6 hours should be allowed for reaction and at higher temperatures, for instance 100 0., from 30 minutes to 2 hours should be allowed. Of course, longer reaction periods may be employed if desired as there is little or no danger of decomposing the product.

The invention will be more particularly illustrated by the following examples in which all parts are by weight unless otherwise indicated.

Example I With 110 g. of p-chlorobenzylamine there is mixed 80 ml. of diethyl glutamate and this mixture allowed to stand at room temperature for 2 days. At the end of this time the mixture is diluted with several volumes of ether, cooled, and the product removed by filtration. This N -(pchlorobenzyl) 2 pyrrolidone 5 carboxamide is then purified by 2 recrystallizations from absolute alcohol.

Example II About 170 g. of p-methylbenzylamine is mixed with 110 ml. of diethyl glutamate and this mixture is allowed to stand at room temperature for 2 days. The reaction mixture is then diluted with 900 ml. of ether and cooled overnight. The resulting crystals of N -(p-methylbenzyl) -2-pyrrolidone-5-carboxamide are collected and purified by 2 recrystallizations from ethyl acetate.

Example III With 7 ml. of diethyl glutamate there is mixed 11 g. of o,p-dimethylbenzylamine and this mixture is allowed to stand for 2 days at room tem- 3 recrystallizations from ethanol-ether solution.

Example IV With 900 ml. of benzylamine there is mixed 550 g. of diethyl glutamate and the resulting mixture heated at about C. on a steam bath for 3 hours. The reaction mixture then cooled to room temperature and 4 liters of ether added.

The mixture is cooled overnight and the crystal- N -benzyl 2- pyrrolidone-5-carboxamide is purified by recrystalliza line; 1 1joductcollected. This tion from ethanol.

Example V A mixture of 5.5 gJof diethyl glutamate and 10 ml. of benzylamine is heated almost to reflux for about 15 minutes. After standing an additional 15 minutes the mixture is cooled and diluted with 50 ml. of ether. After further cooling the crystallin N -benzyl-2-pyrrolidone-5-carboxamide is separated and purified by recrystallization from ethanol.

- Example VI Example VII To 160, m1. of absolute ethanol plus 40 ml. of ethyl alcoholsaturated with HCl gas, there is added 40 g. of 3,3,5-trimethyl-2-pyrrolidone-5- carboxylic acid and this mixture is then refluxed about 2 hours. The reaction mixture is then concentrated to dryness in vacuo and the resulting residue crystallized from 200 ml. of heptane. The resulting crystals are added to 40 ml. of benzylamine and this mixture heated at 160-170 C. for 8 hours. After cooling, the mixture is diluted with 500 ml. of ether and chilled overnight. The crystalline 3,3,5-trimethyl-N -benzyl2$yrrolidone-5-carboxamide is collected and recrystallized from 5000 ml. of water plus ml. of ethanol.

I claim:

1. The new chemical compounds represented by the formula:

in which R represents a lower alkyl radical.

7E 4.4Thaneweompound-.N-fp methylbenzyla za pyrrolidone-Scarboxamide:

5.:fIhe. newwempoundsorepresented by the fore mula I,

in=which R representsia halogen substituent 6; The new compound N "(p=chrobenzy1') 2 pyrrolidone- 5-carbbxamide.

7. The new=compounds represented bjrthez-foi mulair inwhiohR; represents'at least 1 lowera-alliiyl O LHPJNH0Hzj g}: R531 in which R1, R2, R'a andR; [represent members selectedirom the group consisting of hydrogen and loweralkyliradicalsiand5R5 represents "at leastl member selected from :the. groupwconsist-l ing;o:hydrogen,;-1owen-alkyhradicals and-halogen,

in which R6 and R1 are hydrocarbon esterifying radicals and R1, R2,...R3 and R4 are asudefined above, with a compound of, the-formula:

in which R5 is as defined abovei 11. A method of preparing; N -'benzyl-2-pyrr01id0ne.5-carboxamide whiohi comprises reactingLdiethS -I- lutamate-with: benzylamine.

12.A--method of preparing N -(p-ch1orobenzyl) 2 pyrrolidone-5-carboxamide which com DXPiSCfSwIG3C1ZiZ1gkgdi8th5tlglutamate with p-.ch1om-='-- benzylaminew w 13 A{ method f preparing w .1%- (pemethylbena zy1) 2 pyrrolidone-carboxamide which .com-.\ prises reacting diethyl glutamate .with vp-hmethylvbenzylamine.

14. A-.method of ipreparing.,N ?(2,4-dimethyL-. benzylyl- 2 pyrro1idone- 5 carboxamide whichcomprises reacting ,o,p=dimethy1benzylamine with diethyl glutamate.

ROBERT IBRUCEANGIER-n References Cited in the fi1e-of this patent 1 

1. THE NEW CHEMICAL COMPOUNDS REPRESENTED BY THE FORMULA: 